The filing marks the latest stage in a class action lawsuit brought against the company in January 2002. Apple's offer is conditional on its acceptance by the case judge.

The suit demanded that Apple develop a version of its DVD Player application for all G3-based Macs, and support some old graphics chips, including ATI's Rage family, that shipped with early G3-based machines. Apple subsequently added Rage support to Mac OS X 10.1.5.

Since Mac OS X was explicitly stated to run on a listed set of G3-based Macs, it was said that Apple was obliged to ensure all aspects of the operating system worked on those computers, including the first two iMac releases, the original iBooks, the first PowerBook G3s and beige Power Mac G3s.

The suit also requested the court to force Apple to pay damages to users who found that OS X performed more slowly than Mac OS 9. But since that situation arguably applies to almost everyone who's made the upgrade - even with Quartz Extreme acceleration, the Aqua UI feels less responsive than OS 9's UI - the request was never likely to be granted.

While Apple refuses to accept any liability in the matter, the filing is a win for disappointed customers who forked out $129.99 for Mac OS X. The refund offer is open to anyone who bought the OS before 15 May this year, and is made on condition punters send back their Mac OS X CDs and sign an affidavit which states they haven't used the OS in earnest since their bought it, and will not reinstall the OS on their computer in future.

Anyone who wants to keep using Mac OS X can request a $25 money-off voucher to be put toward an Apple Store purchase of $99 or more.

Apple also has to pay legal costs totalling $350,000, but at least it's been spared a day in court. Its offer has to be ratified by the judge hearing the case, which is expected to take place on 2 September. ®